/Engine/Source/Runtime/SlateCore/Public/Fonts/FontMeasure.h
Finds the last whole character index before the specified position in pixels along the string horizontally
The index of the last whole character before the specified horizontal offset
int32 FindLastWholeCharacterIndexBeforeOffset ( const [FText](API\Runtime\Core\Internationalization\FText) & Text, const [FSlateFontInfo](API\Runtime\SlateCore\Fonts\FSlateFontInfo) & InFontInfo, const int32 HorizontalOffset, float FontScale ) const